This invention relates to a flame-resistant composition of (a) a ring-opening polymerization product of a norbornene derivative and (b) a halogen-containing multicyclic compound or bromine-containing aromatic compound and to articles formed from the flame-resistant composition.
The preparation of the cyano derivative of norbornene was described in the article by H. L. Holmes appearing in "Organic Reaction," Volume 4, pages 60 to 173, published in 1948 by John Wiley and Sons Inc. These monomers were obtained by reacting dicyclopentadiene with acrylonitrile or other vinyl compounds containing the nitrile group, by a Diels-Alder reaction. It has been discovered that cycloolefins such as norbornene and the cyano derivative thereof can be subjected to a ring-opening polymerization to form a new type of polymer. The product formed by the ring-opening polymerization of norbornene derivatives containing the nitrile group, such as 5-cyano-bicyclo [2,2,1]-heptene-2, using a tungsten and/or molybdenum catalyst has been reported in U.S. Pat. No. 3,856,758. This product has greater impact strength than polyvinyl chloride resin (PVC) and polypropylene resin (PP). The tensile strength and hardness of the polymerized, ring-opened, nitrile norbornene derivative is comparable to that of PVC and higher than that of PP. Further, the ring-opened polymer displays high heat resistance, owing, in part, to its high glass transition temperature.
It has been shown that other norbornene derivative monomers containing at least one polar group, such as the ester, ether, imide, halogen and the like, group, can be prepared by a Diels-Alder reaction or other appropriate synthesis. These polar group containing norbornene derivative monomers can then be subjected to a ring-opening polymerization reaction using the catalytic system described in U.S. Pat. No. 3,856,758 or Japanese Patent Application Laid-open No. 112500/75, Laid-open Sept. 3, 1975 to provide ring-opening polymerization norbornene derivatives having excellent mechanical properties. It has been found that the ring-opened polymerization product of a norbornene derivative containing at least one polar group has high impact strength at room temperature and low temperatures. Such products also exhibit higher transparency than PVC and PP and also display good moldability. Owing to these and other factors, shaped articles can be formed from such norbornene ring-opened polymeric derivatives as, for example, containers, films, sheets and pipes. The ring-opened products exhibit good workability and can be employed in the molding process widely employed in the field of synthetic resins, such as extrusion molding, injection molding, blow molding and compression molding.
It has long been desired in the plastics industry to produce resinous compositions with good moldability, mechanical strength and high flame-resistant properties. Such plastics are needed in a variety of products such as consumer electrical appliances, heat resistant casings for industry and the like. It has been found that the ring-opened norbornene polymerization products per se, set forth above do not always possess satisfactory flame retardancy.
As a result, certain conventional and other flame retardants have been proposed for incorporation to the ring-opened norbornene derivatives. It has been found that high flame resistance can be obtained by incorporating a halogen-containing phosphate in the ring-opened polymerization product of a norbornene derivative. The composition excels in flame retardancy and does not produce a cross-linked material on working (a gel material) and can successfully be fabricated into various shapes. Unfortunately, the composition does not always possess satisfactory heat resistance.
Attempts to modify the halogen-containing phosphate to improve its heat resistance have proved unsatisfactory. When amounts of halogen in the phosphate are varied in an attempt to improve heat resistance, the resultant composition containing the norbornene polymer forms a gel at the time of blending, and, consequently, its workability markedly deteriorates and the resulting product is discolored. Products made from this composition, therefore, do not have the requisite luster and transparency for practical use.
Attempts have been made to combine a conventional flame retardant commercially employed in olefinic polymers in the ring-opened polymerization products. The resulting products do not have uniformly acceptable properties. For example, compositions obtained by mixing ring-opened norbornene polymerization products with chlorinated paraffin, tetrabromobutane or tetrabromobisphenol A, each conventional flame retardants employed in synthetic resins, are not heat stable. When such compositions are heated at the time of blending or working, a gel is produced. It is difficult to work the gel into a suitable product. Further the resultant product is deeply dicolored and lacks commercial luster and appeal.